If a tyre is under-inflated, or if it experiences a higher load than intended (for example because a neighbouring tyre on the same axle is under-inflated), the tyre wall may deflect more than it was designed to. An over-deflected tyre, when rolling, will experience forces that can potentially cause damage to the tyre. Aircraft maintenance manuals therefore require an aircraft tyre to be replaced if the pressure in that tyre falls below a certain level, or if the differential pressure between a pair of tyres on the same axle exceeds a particular limit.
It is likely that some tyres are replaced under this policy when they have not been over-deflected and therefore will not have suffered any damage. For example, if a neighbouring tyre on the same axle as an under-inflated tyre is sufficiently inflated, the neighbouring tyre may take enough load to prevent either tyre over-deflecting. This situation may particularly occur on aircraft where the main landing gear comprises more than two posts.
The present invention seeks to address this issue by providing a system for detecting and/or monitoring the actual deflection experienced by a tyre. Such a system can advantageously reduce or eliminate the time and material costs associated with replacing tyres which have not suffered damage due to over-deflection. Alternatively or additionally, such a system can advantageously provide a clear indication that a tyre needs to be replaced.